Management of Severe Hyponatremia (119 mmol/L) with Weakness in a Patient on Indapamide
Immediately discontinue indapamide and initiate isotonic saline (0.9% NaCl) for volume repletion, as this represents thiazide-induced hypovolemic hyponatremia requiring urgent but cautious correction. 1, 2
Immediate Actions
Stop the offending agent: Indapamide must be discontinued immediately, as thiazide-like diuretics are a well-established cause of severe hyponatremia, particularly in elderly women 2, 3, 4. This patient's presentation—weakness developing 3 days after starting indapamide with sodium 119 mmol/L and chloride 89 mmol/L—is classic for thiazide-induced hyponatremia 2, 3.
Assess volume status carefully: Look for orthostatic hypotension, tachycardia, dry mucous membranes, decreased skin turgor, flat neck veins, and confusion 5, 6. The combination of low sodium (119 mmol/L) and low chloride (89 mmol/L) strongly suggests volume depletion with cation depletion 2.
Check urine sodium immediately: A urine sodium <30 mmol/L predicts excellent response to isotonic saline with 71-100% positive predictive value 5, 6. This distinguishes hypovolemic hyponatremia (appropriate for saline) from SIADH (requiring fluid restriction) 5.
Initial Fluid Management
Administer isotonic saline (0.9% NaCl) at 15-20 mL/kg/h for the first hour if the patient is hypovolemic, then reduce to 4-14 mL/kg/h based on clinical response 5, 6. Normal saline contains 154 mEq/L sodium and is truly isotonic 6.
Avoid lactated Ringer's solution (130 mEq/L sodium, slightly hypotonic), as it can worsen hyponatremia 6.
Do NOT use 3% hypertonic saline unless the patient develops severe neurological symptoms (seizures, coma, altered mental status) 5, 7. This patient has weakness but no mention of severe neurological symptoms, so isotonic saline is appropriate 5, 6.
Critical Correction Rate Guidelines
Never exceed 8 mmol/L sodium correction in any 24-hour period to prevent osmotic demyelination syndrome 1, 5, 6. This is the single most important safety principle 5.
For this elderly patient, aim for 4-6 mmol/L correction per day (maximum 8 mmol/L in 24 hours), as elderly women are at higher risk for complications 5, 2, 4.
Target serum sodium of 125-130 mmol/L, not normonatremia, in the acute phase 5. The goal is symptom resolution, not complete normalization 5.
Monitoring Protocol
Check serum sodium every 4 hours initially during active correction 5. If the patient were to develop severe symptoms requiring hypertonic saline, check every 2 hours 5.
Monitor for signs of volume repletion: Resolution of orthostatic hypotension, improved skin turgor, moist mucous membranes, stable vital signs 5.
Watch for osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 5.
Track daily weight: Aim for weight loss of 0.5 kg/day in the absence of peripheral edema 5.
Electrolyte Repletion
Replete potassium and magnesium aggressively if deficient, as thiazide-induced hyponatremia often involves cation depletion 2, 4. The low chloride (89 mmol/L) suggests concurrent potassium depletion 2.
Check serum potassium, magnesium, and chloride at baseline and during correction 5.
Alternative Antihypertensive Management
Switch to a non-diuretic antihypertensive once the patient stabilizes 1. Consider:
- Calcium channel blockers (amlodipine, nifedipine) 1
- ACE inhibitors or ARBs (if not already on maximum dose) 1
- Beta-blockers (if compelling indication exists, such as heart failure or post-MI) 1
Avoid thiazide or thiazide-like diuretics permanently in this patient, as recurrence risk is high 2, 3, 4.
Common Pitfalls to Avoid
Do not use fluid restriction in this patient, as thiazide-induced hyponatremia is typically hypovolemic, not euvolemic (SIADH) 5, 6. Fluid restriction would worsen outcomes 5.
Do not correct too rapidly: Overly rapid correction exceeding 8 mmol/L in 24 hours causes osmotic demyelination syndrome, which can be devastating 5, 2.
Do not restart thiazide diuretics even after sodium normalizes, as this patient has demonstrated susceptibility 2, 3, 4.
Do not delay treatment while pursuing extensive diagnostic workup 5, 7. The diagnosis is clear (thiazide-induced hyponatremia), and treatment should begin immediately 5, 3.
Expected Clinical Course
Symptoms should improve within 24-48 hours of discontinuing indapamide and initiating isotonic saline 3, 4. In reported cases, serum sodium improved to 130 mmol/L by day 6 with symptom resolution 3.
Continue monitoring serum sodium for 7 days after correction to ensure stability 5.